1. Field of the Invention
The present invention relates to a data storage device and a method of tracking data stored in the data storage device, and more particularly, to a method of finely tracking a position of data recorded in a data storage medium using scanning probe microscopy (SPM) technology.
2. Description of the Related Art
Generally, a high-density data storage device using SPM technology includes a data storage medium, a probe, an x-y stage, a controller, and a signal processor. Data can be stored in or erased from the data storage medium. The probe includes a tip for recording or reproducing data and a cantilever on which the tip is mounted. The x-y stage moves the data storage medium, and the controller issues commands to control the data storage device. To record or reproduce high-density data, a method of tracking data with high precision is required.
Three different types of conventional methods of tracking a position of data have been employed to record data on or reproduce data from such a high-density data storage device using SPM technology.
First, the position of data can be tracked using a mechanical or electric signal of a data storage medium by distinguishing a signal of recorded data from a signal of reproduced data. This method is proposed in U.S. Pat. Nos. 5,132,934, 5,396,483, 5,856,967, and 6,370,107. The foregoing patents disclose a method of forming metal patterns or mechanical grooves on a data storage medium, but it is difficult to form sufficiently fine patterns or grooves on the data storage medium. Also, since the mechanical grooves themselves serve as a mechanism for recording and reproducing data, the practical applications of this method are limited.
Second, there is a method of modulating a central position of data recorded in a data storage medium by oscillating a probe or the data storage medium, as disclosed in U.S. Pat. No. 5,404,349. This method is based on a principle of modulation and demodulation by oscillating the data storage medium in a high frequency range. However, it is difficult to oscillate the data storage medium in the high frequency range. In addition, a circuit for detecting the oscillation of the data storage medium becomes complicated and detection is delayed owing to the principle of modulation and demodulation.
Third, a method of using a central position of data stored in a data storage medium and a relative displacement of a probe for recording or detecting the data is disclosed in U.S. Pat. Nos. 5,202,879 and 6,195,313, for example. Unfortunately, this method necessarily requires very precise recording of data patterns in the data storage medium. In particular, the method proposed in U.S. Pat. No. 5,202,879 cannot serially track data. Accordingly, the data can only be tracked at a relatively low speed. Thus, a data tracking process becomes very sensitive to the external environment.